1. Field of the Invention
The present invention relates generally to seals, and more particularly to, a seal for an end cap of a bearing assembly.
2. Description of Related Art
Rotating members such as wheel spindles commonly have a bearing assembly around one end thereof to allow the spindles to rotate relative to a fixed member. Typically, a housing such as an end cap is placed over an opening in one end of the bearing assembly to protect the bearing assembly from foreign contaminants and contain lubricant.
At the assembly of a totally sealed bearing assembly, a fixed volume of air is captured inside a cavity of the bearing assembly. The assembly operation seals the bearing assembly before the designed volume is achieved. Therefore, this reduction in volume results in an increase in internal pressure. During the intended use of the bearing assembly, application of load and introduction of relative motion between the rotating members and the inner and outer rolling elements cause gases to volatilize from bearing lubricant and expand due to the change in temperature. The result is an increase in internal pressure of the bearing assembly. In such conditions, a conventional end cap will retain this increased pressure. As a result, two failure modes can be induced: first, the internal pressure may develop to such an extent that the end cap or an opposed dynamic sealing element may be forced from a counterbore position exposing the rotating members and rolling elements directly to exterior contaminants; and second, the increase in internal pressure can cause an increase in the radial load exerted on the rotating members by the dynamic sealing element. This typically causes an increase in power consumption and eventually leads to premature wear of the dynamic sealing element and failure. Failure in the dynamic sealing element results in a loss of lubricant and ingress of contaminants leading to total bearing failure. Furthermore, a bearing assembly that has reached an elevated temperature condition due to routine service will draw a slight vacuum and ingest contaminants if cooled quickly due to a sudden change in environment. Therefore, a need exists for an element which would vent positive pressure and prevent equalization of a negative pressure resulting in ingestion of contaminants.
Solutions to relieve this condition usually require a dynamic sealing element for the bearing assembly to vent across the dynamic sealing interface. This compromises the effectiveness of the dynamic sealing element.